Calibration is a mandatory procedure to enable AI-Traffic available functionalities. Since it is a crucial step of the configuration process, the interface has been designed to be as intuitive as possible also for less experienced users. You can find all the calibration parameters in the sheets "Calibration" and "3D Calibration".
In the drop-down menu on the left side by selecting the panel "Algorithm Parameters" and the panel “Calibration” it is possible to set the real parameters of the camera with respect to the road. A mistake during the configuration of this field negatively affects the results of the calibration process.
Then, you will have to set the following parameters:
Only after you have set "Calibration" parameters you can start with the "3D Calibration" that you can find in the panel "Algorithm Parameters" as well. From the drop-down menu you can choose between two different types of calibration: A) Lines parallel to road and vertical lines B) Lines parallel to road only
The procedures consist in three steps:
This step is common to both types of calibration. As shown in the image on the right, you can use the boundary lines of the carriageway or any other line parallel to the motion direction. Be careful that the lines are drawn with accuracy, since an error in this step may negatively affect the results of the calibration.
As shown in the picture, if there are parallel vertical lines (for instance,street lamps, buildings), you can use them to perform the Step 2 of the calibration. Be careful in drawing lines with accuracy, as a mistake in this step could negatively affect the results of the calibration.
If there are no vertical parallel lines available in the scene or that kind of calibration fails or is imprecise, an alternative way to complete the calibration is shown in the image. You can use parallel lines on the ground to perform the step 2 of the calibration if those are perpendicular to the blue ones from step 1. Be careful to draw the lines accurately, since an error in this step may negatively affect the results of the calibration
You can obtain the best calibration possible through the configuration of camera parameters, namely:
The first can be easily retrieved from the camera data sheets and it is given as an inch fraction (a table for conversion can be retrieved HERE. The latter may also be available on the datasheet, though some cameras may mount lenses with a variable level of zoom (i.e. variable focal length, varifocal). For varifocal cameras, the datasheet provides a range (minimum to maximum focal length, e.g. 5.2-62.4 mm), but the specific value depends on how the lens is configured, either manually (rotating a wheel) or electronically (via software); in this case, keep in mind that a small number means a large field of view with possible distortion of the image, while a large number means maximum zoom.
TIP: If you don’t see the grid or the error you may have forgot to draw the analytic sensor.
Each tile of the grid measures 1x1 meters. If the tiles look small, this may mean that the configured height is too high. Decrease it. If the tiles are too large, it means that the configured height is low and you need to increase it.
In the top figure, the tiles are too large: one runway only covers one tile and one half in width. The with of the car is wrongly estimated to be 60cm. In the bottom figure the height is increased from 3 meters to 8 and the problem is fixed.
Can’t see the error on the top right corner
The focal length and the height are right, the lines are accurate but the configuration is broken:
The grid appears in weird spots (e.g. on the ceiling):